The present invention relates in general to semiconductor devices and, more particularly, a method of forming a sculptured diaphragm.
Semiconductor sensors are comprised of thin diaphragm formed on a semiconductor substrate. The diaphragm is typically formed by etching the back side of a semiconductor substrate to form a cavity and leaving a thin layer of semiconductor material to act as the diaphragm.
The deformation or movement of the diaphragm causes a change in capacitance or resistance. In order to respond to low pressures, the diaphragm thickness is reduced. However, a thin diaphragm causes more nonlinearities to occur in the output due to the presence of nonlinear membrane stresses present on the surface of the diaphragm.
To reduce the nonlinearity, a diaphragm of variable thickness is desirable. Such diaphragms have been fabricated by making certain portions of the diaphragm thicker than others. The thicker portions of the diaphragm are called bosses. This approach allows the fabrication of high output, low pressure sensors with substantially linear outputs.
It would therefore be advantageous to be able to fabricate a sensor with a diaphragm having a thick central boss in a cost competitive manner.